On 10/25/2011 12:19 AM, makarand pradhan wrote:
> (...) I'm
> assuming that the ROOT thread captures the %CPU spent in
> Linux/secnodary and each xenomai thread listed, captures the %CPU in
> primary domain. If a thread transitions to the secondary, then I'm
> assuming that the %util in secondary domain will get accounted
> against ROOT and the actual % usage in primary will get accounted
> against the thread.

You are assuming wrong, the CPU utilization measures the activity of the
linux kernel as a whole, including its idle task. So, the sum of all the
primary mode tasks and of the ROOT task is always 100%.

> Question:
> If the linux process is sleeping, why do I see a CPU util against the
> process? Why is the CPU % util vary based on the activity I do in the
> primary domain?

rt_printf is a primary mode service which causes activity in secondary
mode: the actual printf is done by a plain linux task.


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